netdev - [PATCH net-next 8/8] selftests/net: packetdrill: add tcp_rcv

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Message-ID: <20250711114006.480026-9-edumazet@google.com>
Date: Fri, 11 Jul 2025 11:40:06 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Neal Cardwell <ncardwell@...gle.com>
Cc: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>, 
	Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 8/8] selftests/net: packetdrill: add tcp_rcv_toobig.pkt

Check that TCP receiver behavior after "tcp: stronger sk_rcvbuf checks"

Too fat packet is dropped unless receive queue is empty.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 .../net/packetdrill/tcp_rcv_toobig.pkt        | 33 +++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 tools/testing/selftests/net/packetdrill/tcp_rcv_toobig.pkt

diff --git a/tools/testing/selftests/net/packetdrill/tcp_rcv_toobig.pkt b/tools/testing/selftests/net/packetdrill/tcp_rcv_toobig.pkt
new file mode 100644
index 0000000000000000000000000000000000000000..f575c0ff89da3c856208b315358c1c4a4c331d12
--- /dev/null
+++ b/tools/testing/selftests/net/packetdrill/tcp_rcv_toobig.pkt
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0
+
+--mss=1000
+
+`./defaults.sh`
+
+    0 `nstat -n`
+
+// Establish a connection.
+   +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+   +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+   +0 setsockopt(3, SOL_SOCKET, SO_RCVBUF, [20000], 4) = 0
+   +0 bind(3, ..., ...) = 0
+   +0 listen(3, 1) = 0
+
+   +0 < S 0:0(0) win 32792 <mss 1000,nop,wscale 7>
+   +0 > S. 0:0(0) ack 1 win 18980 <mss 1460,nop,wscale 0>
+  +.1 < . 1:1(0) ack 1 win 257
+
+   +0 accept(3, ..., ...) = 4
+
+   +0 < P. 1:20001(20000) ack 1 win 257
+ +.04 > .  1:1(0) ack 20001 win 18000
+
+   +0 setsockopt(4, SOL_SOCKET, SO_RCVBUF, [12000], 4) = 0
+   +0 < P. 20001:80001(60000) ack 1 win 257
+   +0 > .  1:1(0) ack 20001 win 18000
+
+   +0 read(4, ..., 20000) = 20000
+// A too big packet is accepted if the receive queue is empty
+   +0 < P. 20001:80001(60000) ack 1 win 257
+   +0 > .  1:1(0) ack 80001 win 0
+
-- 
2.50.0.727.gbf7dc18ff4-goog